Ground reservoir for the storage of liquefied gases



1964 c. M. SLIEPCEVICH 3,159,006

GROUND RESERVOIR FOR THE STORAGE 0F LIQUEFIED GASES Original Filed April20, 1960 2 Sheets-Sheet 1 si ma li a 2 INVENTQR. (cdomir 7/7. SizepcewchYM afforneys Dec. 1 1964 c. M. SLIEPCEVICH 3,159,006

GROUND RESERVOIR FOR THE STORAGE OF LIQUEF'IED GASES Original FiledApril 20.- 1960 2 Sheets-Sheet 2 INVENTOR Ceaonzzr 772. Size 06611101;

. %W MYM C'Zilarnaqi United States Patent.

H 3159,,lill6 GROUNT) RESERVOlR F V R THE STORAGE 0F LIQUEFIED GASESCe'domir' M. Siiepcevic'h, Norman, ()kla, as'sign'or to 'ConchInternational Methane Limited, Nassau, Ba-

hainas, a corporation of Bahamas Continuation of abandoned applicationSer. No. 23,439,

Apn Zll, 1960. This application Oct. 4, 1963, Ser. No.

6 Claims. (Cl. 62-45) This application is a continuation of applicationSerial No. 23,439, of Ced'o'rnir M. Sliepcevich, filed April 20, 1960,now abandoned, for Ground Reservoir for the Storage of liquefied Gases.I

This invention relates to the storage of liquefied gases, particularlyliquefied natural "gas "or methane and liquelied petroleum gases such asethane, propane and butane.

It is an object of this invention to produce an inexpensive, efiici'entand -safe storage space for liquefied gases and it is a related objectto produce an underground storage for cold liquefied gases which issimple in consanction, eificient and safe in operation and whichprovides for low heat loss into the storage space thereby to minimizeloss of liquid content material.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, an embodiment of the invention is shown in the accompanyingdrawings, in which:

FIG. 1 is a schematic sectional eievational view of a storage spaceembodying the features of this invention;

FIG. 2 is a schematic sectional view similar to that of FIG. 1 showing amodification in the construction of the storage space;

FIG. 3 is a sectional 'elevational view of a section of the roofemployed in the construction of this invention; and

FIG. 4 is a sectional elevational view of acorner section of a reservoirshowing the portion wherein the roof comes into engagement with theground.

In this specification the expression liquefied 'gas means liquid whichboils at atmospheric pressure at a temperature below the ambienttemperature.

In this specification the expression a hole in the surface of the earthmeans a hollow place in the surface of the earth which has a substantialarea in the plane of the surface in relation to its capacity, i.e. it isnot intended to include narrow shafts or wells. A compact hole means ahole having a small surface in relation to its bulk or volume. This isimportant in storing cold liquids because the rate of heat loss is aminimum when the container has length, breadth and depth of the sameorder of magnitude so that the hole should approximate a sphere,

.It has also been proposed to store liquefied petroleum gas in anunderground storage cavern located in a permeable water bearingformation in which the water in the cavern wall is frozen to render thewall impermeable to the fluids stored." This proposal suffers from thedefect that if no natural cavern is available in the desired location ofthe storage system such a cavern has to be mined "70 and this is anexpensive operation. Furthermore, the shape of large uhdergroun-dcaverns is inherently not Ice Patented Dec. 1, 1964 compact, bothbecause of the way they are formed in nature and because a large cavernwould tend to collapse without internal supporting columns (such as areleft in coal mines for this purpose), due to the unsupported weight ofthe cavern roof, and these supporting columns would have to be oflimited length and therefore, the cavern would have a large diametercompared with its depth and would therefore not be compact.

I have now invented a reservoir which can be constructed cheaply at anytype of site.

This invention provides a reservoir for the storage 'of liquefied gaseswhich comprises a compact hole in the surface of the earth, the earthformation surrounding said hole containing a liquid which will solidifywhen the reservoir is charged with the liquefied gas to be stored, athermally insulated roof completely covering said hole, a gas vent insaid roof and conduit and pumping means for filling and dischargingliquid from said reservoir. This roof is made of solid and impermeablematerial, and is supported at the periphery of the hole without anysubstantial internal supporting columns or other solid internal support.

When such a reservoir is filled with liquefied gas, the liquid in thesurrounding earth formation is solidified and the formation is sealed bythe frozen liquid. Accordingly, the invention ultimately provides areservoir containing a liquefied gas which comprises a hole in thesurface of the earth, the earth formation surrounding said holecontaining a frozen liquid which seals the said formation, a thermallyinsulated roof covering said hole, a gas vent in said roof, liquefiedgas within said hole and conduit and pumping means for filling anddischarging liquid from said reservoir.

The earth formation in which the hole is made must be one containing aliquid which solidifies at the boiling point of the liquefied gas.Normally, this liquid will be water, and, therefore, if the earthformation is a water bearing one, such as wet soil or sand, it can beused without further modification. If, however, the earth formation atthe site where the reservoir is to be built is dry it will be necessaryto impregnate the earth with water or with some other liquid whichsolidifies at the boiling 'point of the liquefied gas. .Such otherliquid might be a crude petroleum oil or a heavy oil fraction orresidue.

The hole may be a naturally occurring one or it may be made artificiallyby excavation or by suitable explosion forces. When working in dry sandit may be desirable to impregnate the area in which the hole is to bemade with water and freeze the water before carrying out the excavation.

The roof over the hole may be made of any suitable lniaterial such assteel, particularly carbon steel, alumimin or wood. In the case of woodit should be suitably sealed at the joints. The roof must be thermallyinsulated to prevent, as far as possible transfer of heat from theatmosphere into the reservoir. This insulation may be on top of the roofor beneath it or both. In the case of insulation beneath the roof, itmay be fixed in contact with the underside of the roof or it may besuspended at short distance, from the underside. Preferably the surfaceof the earth in thene'ighborhood of the perimeter of the roof shouldalso be insulated and this insulation may be continuous with anyinsulation on the top of the roof. A coin-pact hole has a depth of thesame order of magnitude as its width. Since heat loss is a majorproblem, a small hole in the ground will tend to lose too much heat tobe practically feasible; the hole should preferably be at least .100feet in diameter, and in any case, greater than feet. In so large ahole, since sup porting columns would need to be of the same order oflength as the diameter, it is clear that such supporting columns wouldbe very expensive to construct, and would q the accompanying -of theinvention.

. 3 also reduce the valuable storage space. I am aware of the US. patentto Cooper, No. 2,437,909, which uses a fill of detritus to support aroof in a ground storage system for liquefied gas, which both adds tothe expense and greatly detracts from the storage capacity of thesystem.

Suitable thermal insulating-materials for both the roof and the surfaceof the earth around its perimeter are perlite, fiber glass, paperhoneycomb and foam plastics, such as foamed polystyrene and polyurethanefoams. The surface of the earth surrounding the perimeter of the roofmay also be insulated by dry shingle, sand or concrete.

If the structure of the earth formation is such that a considerableamount of liquefied gas is likely to be. lost when it is first chargedinto the reservoir, two courses are open; viz, the earth formationsurrounding the hole may be frozen before any liquefied gas is put intothe v reservoir, or the earth formation surrounding the hole may besealed by a thin metal membrane such as thin aluminum sheet or by alayer of thermal insulation which has the ability of holding theliquefied gas away from the earth. Suitable materials are fiber glass,very fine It should be noted that when a thermal insulation is laidwithin the hole it is only required to act as a temporary barrier and,therefore, need not be of robust construction. Eventually, the liquid,for example the water in the earth formation, freezes and forms apermanent barrier.

With the passage of time as the reservoir is used the temperature of theground outward from the liquefied gas progressively decreases and as aresult the heat leakage inward towards the liquefied gas decreases. withtime the insulation of the ground improves and after several years theheat leakage for all practical purposes becomes negligible. The heatleakage through the roof is reduced as far as possible by the use ofthermal insulation, but in any case is comparatively small becausebecause the roof is in contact only with gas and not with liquefied gas.

The hole in the ground may be of any suitable shape, for example, it maybe a hollowed out basic or a cylindrical or rectangular hole.

The roof must be fitted withv a gas vent which will lead the gasesproduced in the reservoir to some suitable disposalpoint or recoveringplant; for example, it may lead to a flare or to a gas storage system orto a reliquefaction plant. y, Preferably the vent will be fitted with apressure control device which will control the pressure of gas in thereservoir.

perlite or foam plastics, such as those mentioned above.

Thus

The'conduit and pumping means for filling and discharging from thereservoir may be of any suitable type.

Thus a single pipe leading to the bottom of the reservoir may be usedfor both filling and emptying the reservoir,

the latter being accomplished by a gas lift installation;

Alternatively, there may be one inlet pipe and a second outlet pipeconnected with the submerged pump;

'Normally the gas vent and the conduits for filling and discharging thereservoir will pass throughthe roof, preferably through a trunk in theroof. It is possible, however, to take the filling and dischargingconduits through tunnels made'in theside of the reservoir and leading upto the earths surface. j i

The invention will now be described with reference to In-FIG. 1',numeral 1 represents the surface of the earth in which a groundreservoir has been constructed. A basin 2 has been hollowed out of theearth, for example by excavation, and. the surrounding formation 3 hasbeen subjected to continuous cooling by conventional refrigerationmachines so that the waterin' the formation is frozen.

@A'roof 4covers the basin .Z'and is itself covered bya' layer of thermalinsulation 5, for example perlite or fiber drawings which illustratemodifications glass. This insulation is extended around the perimeter ofthe roof to cover the adjacent earth as at 6.

Through the roof runs a filling conduit 7 extending almost to the bottomof the basin, and also a discharging conduit 8 fitted with a submergedpump 9. A vent 10 through the roof allows the exit of gas produced bythe heat leakage into the reservoir. In this manner, the vapor pressurein the space above the liquid gas is maintained slightly aboveatmospheric pressure resulting only in a small upward thrust on theroof, which may accordingly be of relatively light, self-supportingconstruction. It should be noted that at pressures substantially higherthan atmospheric, in the case of a reservoir of such large diameter asthis invention is concerned with, the weight of the roof required tosafely hold the pressure soon becomes so great, as the pressure requiredis increased, that a fabricated roof is impractical to construct, sinceit must have the mechanical strength necessary to support its own greatWeight. For this reason, it was heretofore not considered practical toconstruct a large diameter surface storage reservoir of compact shape.It may, however, be possible toconstruct a roof capable of withstandingsuch higher pressures if the breadth of the hole is small in relation tothe length, allowing for short spans in one direction, i.e., if the holeis not a compact'one, for example as shown in the US. patent toGoldtrap, No.

2,961,840, but then the heat loss becomes so great that it is notfeasible to store extremely cold liquids such as liquid methane. u

The vent to is preferably fitted with a pressure control device asindicated at Ma Liquefied natural gas may be stored in such a reservoirover long periods, and the longer the reservoir is in use, the moreeffective is the thermal insulation of the frozen area 3. The optimumliquid level is shown at 11.

In FIG. 2, the numerals 1, 2, 3, 4, 5, 6, 10 and 11 have the samesignificance as in FIG. 1. However, in this reservoir the initial basin2 was covered with a layer of glass fiber 12 which provided a temporaryinsulation and barrier preventing loss of liquefied natural gas when itwas first charged into the reservoir. In this type of structure, theremight be no need to freeze the surrounding formation 3 prior to chargingthe liquid gas to the reservoir. The slow heat leak into the reservoircauses the surrounding formation to be frozen over a period of time,during which period substantial loss of liquefied gas is prevented bythe glass fiber layer 12. If desired, the glass fiber layer 12 can becovered by a thin film of, for example, paper or aluminum sheet. Insteadof layers of fiber glass in the lining or in the roof insulation, usecan be made of other thermal insulating materials such as "balsa Wood,foamed plastics and the like.

The filling and discharging arrangements of FIG. 2 comprise a singleconduit 13 passing through the roof which can be used either for fillingthrough branch 14 or discharging by means of a gas lift system throughbranch 15.

in the reservoir of the present invention. This roof structure comprisesa steel roof 16 with a layer of insulation 17 suspended therefrombysuitable brackets. The in sulation is preferably impermeable to gasesand may be formed, for example, of foamed plastic with disconnectedpores or filled paperhon'eycombs. The gas space between the roof 16 andthe suspended insulation 17 adds to the thermally insulatingpropertiesof the roof as a whole.

.FIG. 4 illustrates a preferred method of sealing the joint between theroof and the surrounding earth formation. The roof 16 with .itssuspended thermal insulation ,17 is built a small way into the surfaceof the surrounding earth 1. A layer of cement 181is laid on the earthsurface adjacent to the perimeter of the roof and a layer of a thermallyinsulating material 6, such as perlite or fiber glass, is laid on thecement. The portion of the formation in the corner between the roof andthe side of the basin at 19 is kept frozen if necessary by artificialmeans.

One of the chief advantages of the present invention is that very largequantities of liquefied gases can be stored cheaply. Reservoirs of thisinvention may be very large indeed, for example, they can vary from 50feet to 200 feet in diameter. Convenient size is 100 feet in diameter.Similarly in depth they can vary from 50 feet to 200 feet, butconveniently a depth of 70 feet to 200 feet is used. Where the earthsurface is insulated around the perimeter of the roof, the distance forwhich the insulation is required will depend on the particular liquefiedgas being stored and the particular atmospheric conditions prevailing.In general, the ground surrounding the perimeter of the roof will beinsulated to a-distance of 15 feet to 50 feet.

It will be understood that various changes may be made in the details ofconstruction and operation without a departing from the spirit of theinvention, especially as defined in the following claims.

I claim:

1. A reservoir for storing liquefied gas at substantially atmosphericpressure and at a temperature below minus 40 R, which comprises a largecompact, basin-like hole in the surface of the earth, the diameter ofsaid hole at said surface being in the order of at least 75 feet; theearth formation surrounding said hole containing a frozen liquid whichseals said formation at the temperature of said liquefied gas; a roofincluding an impervious structural roof panel which is solid at allnormal ambient temperatures above 32 F. spanning the top of said hole,

said roof including a layer of insulation; supporting means at theperimeter of the hole taking the full weight of the roof in the emptycondition of the reservoir; said roof being in sealed relationship withthe frozen earth surrounding the rim of said hole; said roof being bothgas-and-liquid tight except for a controllable gas vent therein; theinterior of said hole being substantially clear of any solidobstructions for retaining a maximum volume of liquefied gas, and beingsubstantially clear of internal supporting structure for said roof, andmeans for conducting liquefied gas into and out of said hole and meansfor maintaining the vapor pressure of boiling liquefied gas in saidreservoir at slightly above atmospheric pressure.

2. The invention according to the preceding claim 1, said layer ofinsulation being suspended below and supported by said panel.

3. A reservoir for the storage of liquefied gases which comprises a holedefined in the surface of the earth, a layer of a thermal insulatingmaterial located adjacent the surfaces defining said hole and a thinmetal membrane covering said insulating layer, the earth formationsurrounding said hole containing a liquid which solidifies at theboiling point of the liquefied gas to be stored, a thermally insulatedroof completely covering said hole and made of a material which is solidat ambient temperatures, a gas vent, and conduit and pumping means forfilling and discharging liquid from said reservoir, said thermalinsulating material being glass fiber material.

4. The invention according to claim 1 said layer of insulating materialbeing above and supported by said panel.

5. The invention according to claim 1, and a layer of liquid imperviousmaterial lining the interior surface of said compact hole.

6. The invention according to claim 5, said layer impervious materialbeing a thin metal membrane.

References Cited by the Examiner UNITED STATES PATENTS 2,241,843 5/41Buddrus et al 62-45 2,437,909 3/48 Cooper 6245 2,705,414 4/55 Rose 220-92,796,739 6/57 Meade et a1. 6254 2,911,125 11/59 Dosker 6245 2,961,84011/ Goldtrap 6245 3,092,933 6 63 Closner et al 220-18 ROBERT A. OLEARY,Primary Examiner.

1. A RESERVOIR FOR STORING LIQUEFIED GAS AT SUBSTANTIALLY ATMOSPHERICPRESSURE AND AT A TEMPERATURE BELOW MINUS 40*F., WHICH COMPRISES A LARGECOMPACT, BASIN-LIKE HOLE IN THE SURFACE OF THE EARTH, THE DIAMETER OFSAID HOLE AT SAID SURFACE BEING IN THE ORDER OF AT LEAST 75 FEET; THEEARTH FORMATION SURROUNDING SAID HOLE CONTAINING A FROZEN LIQUID WHICHSEALS SAID FORMATION AT THE TEMPERATURE OF SAID LIQUEFIED GAS; A ROOFINCLUDING AN IMPERVIOUS STRUCTURAL ROOF PANEL WHICH IS SOLID AT ALLNORMAL AMBIENT TEMPERATURES ABOVE 32*F. SPANNING THE TOP OF SAID HOLE,SAID ROOF INCLUDING A LAYER OF INSULATION; SUPPORTING MEANS AT THEPERIMETER OF THE HOLE TAKING THE FULL WEIGHT OF THE ROOF IN THE EMPTYCONDITION OF THE RESERVOIR; SAID ROOF BEING IN SEALED RELATIONSHIP WITHTHE FROZEN EARTH SURROUNDING THE RIM OF SAID HOLE; SAID ROOF BEING BOTHGAS-AND-LIQUID TIGHT EXCEPT FOR A CONTROLLABLE GAS VENT THEREIN; THEINTERIOR OF SAID HOLE BEING SUBSTANTIALLY CLEAR OF ANY SOLIDOBSTRUCTIONS FOR RETAINING A MAXIMUM VOLUME OF LIQUEFIED GAS, AND BEINGSUBSTANTIALLY CLEAR OF INTERNAL SUPPORTING STRUCTURE FOR SAID ROOF, ANDMEANS FOR CONDUCTING LIQUEFIED GAS INTO AND OUT OF SAID HOLE AND MEANSFOR MAINTAINING THE VAPOR PRESSURE OF BOILING LIQUEFIED GAS IN SAIDRESERVOIR AT SLIGHTLY ABOVE ATMOSPHERIC PRESSURE.